Cerebellar Cortical Cell Layers



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Cerebellar Cortical Cell Layers

Cell Layers

Components

Characteristics

Molecular Layer

  • The most superficial layer

  • Sparsely cellular

  • Synaptic layer




Stimulatory components

Axons (parallel fibers) of Granule cells

  • Arise from Granule cells at the Granular layer

  • The axons bifurcate at this level, giving rise to 2 horizontal fibers

  • Generate tens to thousands of synapses with the

    • Purkinje cell dendrites

    • Stellate cells

    • Basket cells

    • Golgi cells

Climbing fibers

  • Arise from Inferior Olivary Nucleus of the Medulla Oblongata

  • Runs parallel to the dendrites of Purkinje cells

  • Stimulate Purkinje cells

  • Appears as thin black line around the dendrite of Purkinje cell in Renson’s method

Inhibitory components

Stellate cells

  • Sparsely scattered

  • Small cell with branching of dendrites

    • Makes it appears like a star

  • Unmyelinated fibers runs parallel to the cerebellar folia

Basket cells

  • Special species of stellate cells

  • Close to the Purkinje cells

  • Axons run transversely in the molecular layer

  • Arborized around the Purkinje cells

  • Inhibit activity of Purkinje cells in coordinating muscular activity

Dendrites of Purkinje cells

  • Arises from the Purkinje cells of Purkinje layer

  • Each Purkinje cell gives rise to 2-3 main dendrites directed to the Molecular layer

  • Arborization of Purkinje cell dendrites give a distinctive characteristic of fan-shaped fibers

  • Purkinje cell dendrites run parallel to climbing fiber

Purkinje’s Layer

  • Middle layer

  • Discontinuous layer

  • Single row of cells which are

    • Large

    • Flask-shaped

Purkinje cells

  • Dendrites

    • Give rise 2-3 dendrites

    • Projected to Molecular layer

    • Arborized into tens to thausands of smaller branching

    • Build synapses with

      • Stellate cells

      • Basket cells

      • Golgi cells

      • Axons of granule cells

      • Climbing fibers

  • Axons

    • Projected downward into Granular layer into medullary core

    • Marks the beginning of cerebellar outflow

    • Project upon

      • Deep cerebellar nuclei

      • Extracerebellar targets

  • Sends impulses outside the cerebellum

  • Inhibitory neurotransmitter always GABA

Granular Layer

  • Receive major input into the cerebellum




Mossy fiber

  • Terminations of fibers coming into the cerebellum

Olivocerebellar fiber

  • Fibers that constitute the Climbing fiber at the Molecular layer

  • The only fiber that does’nt terminate at the Granular layer

Granule cells

  • Sends axons into the Molecular layer

  • The axons bifurcate at the level of Molecular layer giving rise to horizontal layers

  • Makes synapses with

    • Purkinje cell dendrites

    • Stellate cells

    • Basket cells

    • Golgi cells

Golgi Type II cells

  • Located close to the Purkinje cells

  • Larger in size compared to Granule cells

  • Dendrites arborized at the Molecular layer

  • Produce synapses with Granule cells at the Gromeruli of Granule layer

  • In each of 10 Purkinje cells there’ll be 1 Golgi Type II cell

Cerebral Neocortical Cell Layers

Cell Layers

Components

Molecular/Plexiform Layer

  • The most superficial layer

  • Contains axons and dendrites of cortical neurons which are synapsing with each other

  • Sparse nuclei cells are neuroglia, occasionally Horizontal cell of Cajal

External/Outer Granular Layer

  • Closely packed small neuron




External Pyramidal Layer

  • Contained numerous

    • Smaller Pyramidal/Betz cells

      • Shape of a pyramid

      • Apex directed outwards (to the Molecular layer)

        • With apical dendrite runs upward

      • Periphery gives rise to the horizontally located basal dendrites

      • Multipolar in nature

    • Granule cells

    • Cells of Martinotti

Internal Granular Layer

  • Chiefly composed of Stellate cells

    • Stacked closely together




Internal Pyramidal/Ganglionic Layer

  • Medium and large sized Pyramidal/Betz cells

  • Intermingled with Granule cells




Multiform Layer

  • Contained

    • Fusiform cells

    • Various other kind of cells






Phylogenetics and Structural Division of Cerebral Cortex

Cerebral Cortex

Allocortex/Paleocortex

  1. The oldest part of cerebral primodial cortex

  2. Consists only 1/12 of total cerebrum

  1. Molecular/Plexiform Layer

  2. External/Outer Granular Layer

  3. External Pyramidal Layer

Isocortex/Neocortex

  • Youngest part of cerebrum

  • Consists of 11/12 of total cerebrum

Homocortex

  • The most common

  • Makes up most of major part in

    • Frontal lobe

    • Parietal lobe

    • Temporal lobe

  1. Molecular/Plexiform Layer

    1. Layer of Associative function

    2. Cajal cells

    3. Functional neurons

  2. External/Outer Granular Layer

    1. Layer of Receptory function

    2. Very numerous neurons

    3. Fibers

      1. Dendrites

        1. Projected to the molecular layer

      2. Axons

        1. Projected

          1. White matter

          2. Turn back to Molecular layer

    4. Golgi Type II cells

  3. External Pyramidal Layer

    1. Layer of Associative function

    2. Pyramidal/Betz cells

      1. Dendrites run toward Molecular layer

      2. Axons contact the Subcortical nuclei

    3. Golgi Type II cells

    4. Cell of Martinotti

  4. Internal Granular Layer

    1. Layer of Receptory function

    2. Golgi Type II cells

  5. Internal Pyramidal/Ganglionic Layer

    1. Same to that of External Pyramidal layer

  6. Multiform Layer

    1. Irregular fusiform and Angular cells

Heterocortex

  • All 6 layers are developed

  • Difference in layer

    • External Pyramidal layer

    • Internal Granular layer

    • Internal Pyramidal/Ganglionic layer

Mortor Cortex/Agranular Type

  • Localized at Area 4-6 (Precentral gyrus)

  • Well developed

    • External Pyramidal layer

    • Internal Pyramidal/Ganglionic layer

  • Poorly developed

    • Internal Granular layer

Sensory Cortex/Granular Type

  • Localized at

    • Area 3,1,2

      • Postcentral gyrus

    • Area 41,42 of Temporal lobe

      • Auditory cortex

    • Area 17-19 of Occipital lobe

      • Visual cortex

  • Well developed

    • Internal Granular layer

  • Poorly developed

    • External Pyramidal layer

    • Internal Pyramidal/Ganglionic layer

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